Bob Eager wrote:
On Sun, 22 Jan 2017 11:35:42 +0000, Dave Plowman (News) wrote:

In article ,
Chris Hogg wrote:
Ah - overloooked that the wireless requirement is a must.

I think I might have had a bit of trouble getting octal valves into
the bell push ...

Indeed, but there were some very small valves available to the public
in the early 1950's before transistors came along later in the decade.
I remember acorn valves, but there was also a little triode about 3 cm
long and the thickness of a pencil, IIRC. May have been gas-filled.
Both types were used in radio controlled model aircraft.
http://www.r-type.org/articles/art-151.htm

The real problem with valves was the power supply for the portable bit.
Like the bell push in this instance.

I'm old enough to just remember valve radio mics. But can't remember
what batteries they used.

Probably used the B7G 'battery' valves (e.g. DF96). 1.4v filament and 90v
anode.

Or even the car radio ones which used 12 volt 'HT' as well as 12 volt
filaments.

--
Chris Green
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